This invention relates generally to imaging systems capable of operation in multiple modalities, and more particularly to an apparatus and method for determining the effectiveness of an image transformation process.
Multi-modality imaging systems are capable of scanning using different modalities, such as, for example, Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), and Computed Tomography (CT). Conventional PET/CT imaging systems experience image quality that is highly affected by physiological patient motion. The quality of the acquired images may affect patient diagnosis.
Patient organ and lesion motion can be a significant source of image quality degradation. Respiratory motion is the most common involuntary motion encountered in PET/CT due to the required duration of PET scanning necessary to obtain clinically useful information. The respiratory motion may be particularly detrimental when a physician is determining the size of a lesion, determining the location of the lesion, or quantifying the lesion. By employing a cardiac and/or respiratory gating protocol during scan acquisition, images may be classified according to the physiological position in the cardiac/respiratory cycle. The gating technique can aid in correction for motion artifacts in images. Also, the image pathway of the nodule or other features of interest may be tracked.
Conventional methods for compensating for respiratory motion, such as by reducing the respiratory motion related artifacts, include using a device that measures an external respiratory signal to gate the PET data. During operation, the PET data is gated into separate bins over the respiratory cycle based on the respiratory signal. Given regular breathing cycles and sufficient imaging time-per-bin, the PET images will include the feature of interest.
However, while conventional methods are useful in reducing imaging artifacts, it is difficult in general for an operator to determine the effectiveness of the conventional image registration process. Specifically conventional imaging systems do not provide feedback to the operator to allow the operator to determine the effectiveness of a data or image transformation process and determine the accuracy of a transformation with regard to the size or location of the lesion of interest.